Many types of input devices may be used to provide input to computing devices, such as buttons or keys, mice, trackballs, joysticks, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation. Typically touch screens can include a touch sensor panel, which may be a clear panel with a touch-sensitive surface, and a display device that can be positioned behind the panel so that the touch-sensitive surface substantially covers the viewable area of the display device. Touch screens allow a user to provide various types of input to the computing device by touching the touch sensor panel using a finger, stylus, or other object at a location dictated by a user interface being displayed by the display device. In general, touch screens can recognize a touch event and the position of the touch event on the touch sensor panel, and the computing system can then interpret the touch event in accordance with the display appearing at the time of the touch event, and thereafter can perform one or more actions based on the touch event.
Touch sensor panels can be formed from a matrix of row and column traces, with sensors or pixels present where the rows and columns cross over each other while being separated by a dielectric material. Each row can be driven by a stimulation signal, and touch locations can be identified through changes in the stimulation signal. Typically, a touch location is sensed based on an interference of the stimulation signal, such that a touch location may correspond to a location where the stimulation signal is the weakest. Touch sensor panels may generally be configured to detect touches from a user's fingers, which generally have a surface area that contacts the touch sensor panel to disturb the stimulation signal sufficiently for touch location to be recognized.
In some instances, computing devices incorporating touch screens may be configured to detect one or more gestures as user inputs. For example, a first type of finger movement, such as a user moving two fingers away from each other may indicate a first type of input (e.g., a zoom-in command), whereas a second type of finger movement, such as a user moving two fingers towards each other may indicate a second type of input (e.g., a zoom-out command). However, in some instances, if a user begins a gesture just outside of the touch screen sensing region, such as towards an edge of the device, the gesture may be difficult to detect because only a portion of the gesture may be detected by the touch screen. In these instances, computing devices may sense inputs that may be different from a user's intended input.